The polvalent vaccines, e.g. the diphtheria-tetanus-pertussis (in the following: Di-Te-Pe) vaccine, play an important role in the extended vaccination program of the World Health Organization (WHO). The aim of this program is to prevent the most dangerous infectious diseases of childhood by vaccination. However, the effectivity of the vaccines commercially available at present is diminished during storage. Particularly under tropic conditions, these Di-Te-Pe vaccines can only be stored for a very short time period; as a consequence of the heat sensitivity of the pertussis component these are only stable for about 1 to 2 weeks.
During the past years, the inventors have studied the stability of the pertussis and Di-Te-Pe vaccines in detail [Csizer Z., Joo I., Zsidai J., Hegedus L.: J. Biol. Standard 1, 347 (1973); Csizer Z., Zsidai J., Joo I.: Atca Microbiol. Acad. Sci. Hung. 22, 83 (1975); Csizer Z., Zsidai J., Joo I.: Acta Microbiol. Acad. Sci. Hung. 25, 1 (1978)] and carried out 400 active immunization experiments on mice by using 53 pertussis strain suspension mixtures within the period from 1960 to 1973. It was determined by the statistical analysis of these investigations that, when stored at 5.degree. to 10.degree. C., the activity of the suspensions decreased after 8 years below the value of 4 international units (IU) which is a single human dose for immunization. From 1968 to 1974, 207 active immunization experiments were carried out by using 21 Di-Te-Pe vaccines on mice. It could be stated from the statistical analysis of the results that, when stored at 5.degree. to 10.degree. C., the activity after 6 years of the pertussis component meets the international and domestic requirements [WHO Techn. Rep. Ser. 638, 37 (1979); Hungarian Pharmacopoeia VI. (1967)]. The mean decrease per one year in the activity of the pertussis strain suspension mixtures is 1.01 IU, while that of the pertussis component of the Di-Te-Pe vaccines is 0.35 IU. Thus, a storage at 5.degree. to 10.degree. C. is suitable to maintain the activity. When stored at 37.degree. C., the activity of the vaccines significantly diminishes within 2 weeks, and even this storage temperature is also difficult to assure under tropical conditions.